4M Knowledge base - papers

V. Piotter, G. Finnah, K. Plewa, R. Ruprecht, J. Hausselt
Forschungszentrum Karlsruhe, Institute for Materials Research III, P.O. Box 3640, 76021 Karlsruhe, Germany

Abstract

In recent years Microsystems Technology products made by thermoplastic injection moulding have steadily entered the worldwide market, and this trend will certainly continue in the next years. On the other hand, there is still a lack of methods for the processing of materials other than thermoplastics, and there is also the necessity to reduce assembly expenditures.

To improve the materials variety the so-called Micro Powder Injection Moulding (MicroPIM) process facilitates a medium- and large-scale fabrication technology for metal and ceramic micro components. Examples are micro gear wheels manufactured on a specially equipped micro injection moulding machine. Minimum dimensions achieved so far are 50μm of part thickness or minimum structural details of less than 10μm. Densities up to 99% of the theoretical values were achieved depending on the particular powder applied. Typical materials are oxide ceramics, conductive ceramics, alloyed steels, or hard metals.

A remarkable new approach is the realization of material combinations like conductive/non-conductive or magnetic/non-magnetic within one singular part by two-component MicroPIM. The main technical challenges are the process parameters which have to be suitable for both materials and the question of adhesion in micro areas. As merging and shaping takes place simultaneously, expensive mounting steps can be omitted.

G. Tosello (a), A. Schoth (b), H.N. Hansen (a)

(a) Technical University of Denmark (DTU), Department of Mechanical Engineering, Produktionstorvet, Building 427S, DK-2800 Kgs. Lyngby, Denmark
(b) Laboratory for Process Technology, Department of Microsystems Engineering (IMTEK), University of Freiburg, George-Koehler-Allee 103,79110 Freiburg, Germany

Abstract

In polymer micro manufacturing technology, software simulation tools adapted from conventional injection moulding can provide useful assistance for the optimization of moulding tools, mould inserts, micro component design, and process parameters. Conventional implementation methods of simulation are not suitable for micro injection (μIM) application and are limiting the possibility to extend the use of existing packages for the modelling and the simulation of polymer micro parts. Different strategies optimized for the set-up the simulation of a miniaturized part with micro features are presented. Model design and mesh issues are discussed, as well as dynamic implementation of the flow constrains for the creation of an effective interface between the machine and the polymer flow in the simulation software. The results of the different methods are evaluated by means of a quantitative study which compares the simulated results and the actual micro injection moulding experiments.

V. Piotter, K. Plewa, J. Prokop, A. Ruh, H.-J. Ritzhaupt-Kleissl, J. Hausselt
Forschungszentrum Karlsruhe, Institute for Materials Research III P.O. Box 3640, 76021 Karlsruhe, Germany

Abstract

Although microsystems technologies products have been steadily launched worldwide markets the development and improvement of manufacturing processes suitable for medium or large-scale production is still one of the most important prerequisites.
A well-known technology to meet such demands is micro injection moulding which has already reached an industrial viable status for polymeric materials. Nevertheless, there is still a lack of methods for the processing of materials with a wider range of properties.
A promising option to close this gap, development of the so-called MicroPIM process to facilitate the fabrication of metal and ceramic micro components was started.
Presently, the smallest dimensions achievable are 25-50μm of part thickness or minimum structural details of less than 5μm. Theoretical densities of up to 99% were achieved depending on the particular powder applied. As further improvement, the technology to produce rotational-symmetric parts by making use of a special head spindle system has been developed.
To enlarge the application possibilities of MicroPIM further, micro two-component injection moulding enables, for example, the fabrication of micro components consisting of two ceramic or metal materials with different physical properties and, not less important, significantly minimises assembly expenditure.

Prof. Dr.-Ing. Dr.-Ing. E.h. Walter Michaeli, Dipl.-Ing. Dirk Opfermann
Institute of Plastics Processing (IKV) at RWTH Aachen University, 52062 Aachen, Germany

Abstract

The miniaturisation of technical products becomes more important in many technological areas. Many functions can be optimised by the use of micro systems. On less space more functions can be integrated. In the field of medical technology miniaturisation means also new methods of treatment with fewer side effects on the patient. New cures are being developed as a result of the miniaturisation of medical instruments, such as the key hole surgery. Polymers are spread widely in the field of medical applications. Since plastics are a relatively cheap material and polymer parts can easily be reproduced in high series and accuracy, for examples by injection moulding, their use as disposable articles is predetermined. Polymer materials offer a wide range of properties that can be chosen according to the functional necessities.

C.A. Griffiths, S.S. Dimov, E. B. Brousseau and M. S. Packianather
Manufacturing Engineering Centre, Cardiff University, Cardiff CF24 3AA, UK

Abstract

Micro injection moulding as a replication method is one of the key technologies for micro manufacture. The understanding of process constraints for a selected production route is essential at both the design stage and during mass production. In this research, an existing Finite Element Analysis (FEA) system is used to study the effects of four process parameters, namely melt and mould temperature, injection speed and part thickness. A special attention is paid to the melt flow sensitivity when filling micro channels, particularly the factors affecting shear rate and flow front temperature. The results obtained from two different simulation models are presented for two polymer materials, PP and ABS and conclusions are made about the important factors affecting part quality.